The objective of this research is the development of new methodology for the detection, identification, and quantitation of organic and inorganic substances which either promote or inhibit the growth of tumors in humans. Specifically, we propose to design, construct, and evaluate a new ion source for chemical ionization mass spectrometry (CIMS) which: (1) can operate over a pressure range from 10 to the minus 2nd power torr to 1 atmosphere; (2) possesses good sample sensitivity at the subpicogram (femtogram) level; (3) affords intense beams of both positive and negative ions; (4) facilitates the analysis of both volatile and nonvolatile organic and inorganic residues; (5) can be interfaced directly to either liquid or gas chromatographic equipment. The above source will be operated in the chemicl ionization mode and will employ either a Townsend or Glow electrical discharge to generate an electron beam. At high pressures (1-760 torr) in a closed source the Townsend discharge produces an abundance of low energy electrons that can be used to generate either positive or negative ions from a variety of reagent gases. In a glow discharge with argon at somewhat lower presssures (10 to the minus 2nd power torr) high energy Ar plus ions are produced. By accelerating these ions onto a cathode (solid probe) containing the sample we expect to be able to sputter neutrals and ions off the cathode surface. Further ionization of the sputtered neutrals by the CI process should generate an intense sample ion beam.